A redstone system could be used to open a door when they through an item into a hopper and on the other side of the door could be a sell sign that buys one dirt and opens a trap door teleporting them away. I can so it for you if you want.

A redstone system could be used to open a door when they through an item into a hopper and on the other side of the door could be a sell sign that buys one dirt and opens a trap door teleporting them away. I can so it for you if you want.

I have made stuff that do things when you buy or sell to a shop so it isn't that hard. I can make a demo of it if you want to see.

How do you intend to stop people from being able to use blocklag to break the door and hit the sign? Or have one person put in an item and have 5 other people go through the door with him at the same time?

Forgot one line. The second line is 1. Slot all is correct though. I forgot that.

The chest would have absolutely nothing inside, if he's using a buffer system. Also what if he got rid of the buffer system and in slot 6 (<-- or whatever slot) had lapis dye inside and I wanted to sell you some wool? Wouldn't work because he's already got the dye in there, the only thing that can be sold now is lapis.

Nope, using block lag non-buyers can get through. Or you can have the door open when somebody throws an item or whatever, and 10 people can walk right in while that one person is using it. Also what if the person doesn't have dirt with him, he just lost out on money.

-sounds like a good idea. The dirt shop could hide itself and open up the chest with the sell sign.

-That is a good point. Maybe a player checker of some sort could do this job. Also since who can enter and who actually enters will be logged, cheaters will be caught easily.

-I don't think block lag will be an issue since the transaction would take place on the server and the lag would just confuse the server momentarily.

I've tested it, if you break a block without build perms and click on a shop sign, it also registers that you clicked the sign along with replacing the block, allowing that you happen. You could have the player walk around corners or something, maybe around a wall so by the time they actually get their block lag would have been fixed?

I don't really see a way to check players which prevents all but one from entering.